A multistage air compressor disclosed in Japanese Unexamined Patent Application Publication No. 2010-059917 includes a drive unit, a low-pressure side compression unit, a high-pressure side compression unit, an air tank, and a joint. The low-pressure side compression unit and the high-pressure side compression unit are connected to each other. Each of the low-pressure side compression unit and the high-pressure side compression unit is adapted to be driven by the drive unit, such as a motor, and to generate compressed air. The air tank is adapted to reserve the compressed air generated by the high-pressure side compression unit. The joint has a decompression valve for decompressing the compressed air reserved in the air tank, so that the compressed air can be taken off from the air tank. In this type of air compressor, a socket is connected to the joint to discharge the compressed air to a pneumatically operated fastener driving tool.
Such an air compressor serves as a power source for a pneumatic tool mainly used in construction work. Normally, two types of air compressor are available. One is used in a work site where a relatively great amount of air is consumed. This type of air compressor includes two or more air tanks and two or more handles, and the user needs to carry the air compressor with both hands. Another is generally used for a pneumatic tool for interior work. This type of air compressor includes a single air tank, and is compact and lightweight. The user can carry the air compressor with a single hand.